Field of the Invention
The invention relates to a turbomachine, especially a steam turbine, having a casing and an inflow region for working fluid which is formed at least in part by the casing. The invention also relates to a method for cooling at least one component associated with an inflow region of a turbomachine.
The use of steam at relatively high pressures and temperatures, especially at so-called supercritical steam conditions with a temperature of, for example, above 550.degree. C., contributes to an increase in efficiency of a steam turbine. The use of steam in such a steam condition makes increased demands on a steam turbine supplied with the steam, especially on steam-turbine components adjoining the inflow region for the working fluid, such as a wall of the casing and a turbine shaft.
An article entitled "Dampfturbinen fur fortgeschrittene Kraftwerkskonzepte mit hohen Dampfzustanden" [Steam turbines for Advanced Power-Station Concepts with High Steam Conditions] by D. Bergmann, A. Drosdziok and H. Oeynhausen, in Siemens Power Journal 1/93, pp. 5-10 describes a rotor shield configuration with swirl cooling. With swirl cooling, steam flows into a region between the rotor shield configuration and a rotor in the direction of rotation of the turbine shaft through four tangential holes in the rotor shield configuration. In the process, the steam expands, the temperature falls and the rotor is thereby cooled. The rotor shield configuration is connected in a steam-tight manner to a fixed-blade row. Through the use of the swirl cooling, it is possible to achieve a reduction in the temperature of the rotor in the region of the rotor shield configuration of about 15 K. A more detailed explanation of that rotor shield configuration, which surrounds the turbine shaft with a clearance and is connected to radially inner ends of the fixed blades of the first fixed-blade ring, is given in European Patent 0 088 944 B1. Nozzles are fitted in the rotor shield configuration and, as viewed in the direction of rotation of the shaft, they open tangentially into an annular passage formed between the shaft and the shaft shield configuration. A further example of a rotor shield configuration can be taken from German Published, Non-Prosecuted Patent Application DE 32 09 506 A1.
Swiss Patent No. 430 757 describes a shielding element in the inflow region of a steam turbine. That shielding element is connected with a feed which is located centrally in the inflow region, i.e. in the hot working steam flow. That feed acts as a mounting for the shielding element.
German Published, Non-Prosecuted Patent Application DE 34 06 071 A1 describes a double-flow steam turbine, which has a shielding element for the turbine shaft in an inflow region for hot steam. That shielding element is connected with the housing through the first rows of rotating-blades. A gap is formed between the shielding element and the turbine shaft. The shielding element has an opening in its center for the hot steam, so that the hot steam flowing in the gap feeds back into the main stream of hot steam before the first row of rotating-blades.